The present invention relates to a burner apparatus and a method of operating the burner apparatus.
A burner is known to produce oxides of nitrogen (NOx) during the combustion of fuel. NOx is generally produced by the combination of oxygen and nitrogen molecules supplied by the oxidant. It is sometimes desirable to reduce the level of NOx.
In accordance with the present invention, a method is provided for operating a burner apparatus. The burner apparatus defines a reaction zone and a process chamber adjoining the reaction zone. The burner apparatus includes a plurality of structures, to include an oxidant supply structure, which directs oxidant to flow into the reaction zone, and a primary fuel supply structure, which directs primary fuel to flow into the reaction zone for mixing with the oxidant to create a combustible mixture in the reaction zone. The burner apparatus further includes an igniter to ignite the combustible mixture in the reaction zone and initiate combustion that provides thermal energy to the process chamber. The burner apparatus also includes a secondary fuel supply structure that directs secondary fuel to flow into the process chamber.
The method includes providing flows of oxidant and fuel through the supply structures in a plurality of distinct modes. The modes include a startup mode. In the startup mode, flows of the oxidant and the primary fuel are ignited by the igniter and are provided simultaneously with a flow of the secondary fuel until the process chamber reaches the auto-ignition temperature of the secondary fuel. The modes further include a subsequent mode in which flows of the oxidant and the secondary fuel are provided simultaneously to the exclusion of a flow of the primary fuel.
The present invention also provides a particular configuration for the primary fuel supply structure in the burner apparatus. In accordance with this feature, the primary fuel supply structure is configured to direct the primary fuel into the reaction zone in a first concentration of fuel in a first region of the reaction zone remote from the secondary fuel inlet. The primary fuel supply structure further is configured to direct the primary fuel into the reaction zone in a second, greater concentration of fuel in a second region of the reaction zone between the first region and the secondary fuel inlet. As a result, combustion of the second concentration of fuel provides sufficient thermal energy to auto-ignite the secondary fuel adjacent to the secondary fuel inlet in the process chamber.
In accordance with another feature of the invention, the fuel supply structure includes a joint having an inlet communicating with the source of fuel, a primary fuel outlet communicating with the reaction zone, and a secondary fuel outlet communicating with the process chamber. The fuel line joint directs fuel from the inlet to the primary fuel outlet along a first flow path at a first flow rate. The joint further simultaneously directs fuel from the inlet to the secondary fuel outlet along a second flow path at a second flow rate. For a given inlet flow rate, the joint directs the fuel such that the ratio of the first flow rate to the second flow rate varies inversely with the inlet flow rate.